The present invention relates to a beer vending machine which stores beer in beer barrels cooled in a refrigerator and serves the beer to a cup by further cooling the same by passing through a cooling coil, and a method of controlling pressure in the beer barrel.
FIG. 4 is a schematic drawing showing the structure of a conventional beer vending machine. Referring to FIG. 4, a cylinder 1 stores carbon dioxide gas therein. A gas regulator 2 regulates the pressure of the carbon dioxide gas on a secondary side thereof at a certain value. A pressure sensor 3 on the secondary side of the gas regulator 2 monitors the secondary pressure of the carbon dioxide gas. The carbon dioxide gas fed through the regulator 2 is distributed to beer barrels 7a, 7b through a gas distributor 4. Gas valves 5a, 5b disposed in gas feed pipes between the gas distributor 4 and the beer barrels 7a and 7b operate to supply and stop the carbon dioxide gas. Check valves 6a and 6b are disposed in the gas feed pipes near the beer barrel 7a and 7b. A temperature sensor 8 monitors the temperature of the beer stored in the barrels 7a and 7b.
The beer barrels 7a, 7b are stored and cooled in a refrigerator. For vending the beer, one of the gas valves 5a and 5b is opened and the carbon dioxide gas is fed through the gas distributor 4 to either one of the beer barrels 7a or 7b at a predetermined pressure regulated by the gas regulator 2 and monitored by the pressure sensor 3. The beer stored in the barrel 7a or 7b is pushed out by the pressure of the carbon dioxide gas, cooled while flowing through a cooling pipe (not shown) connected to a piping on the secondary side of the barrels 7a and 7b, and served to a cup or cups. The check valves 6a, 6b are disposed between the gas valves 5a, 5b and the beer barrels 7a, 7b to prevent the beer from flowing back to the gas distributor 4.
The preferable storing temperature of the beer is 25.degree. C. or lower before the beer barrel is stored in the refrigerator of the vending machine, and in the refrigerator, the beer is cooled down in a range of 10.degree. to 12.degree. C. At the exit end of the cooling pipe, i.e. where the beer is poured into the cup, the beer, even if supplied at 25.degree. C., is cooled down into 1.degree. to 5.degree. C.
When the beer temperature monitored by the temperature sensor 8 is outside the range between 10.degree. and 12.degree. C., the gas regulator 2 is manually adjusted to regulate the gas pressure and to push out the beer under the pressure suitable to the beer temperature.
It is preferable to keep the internal pressure in the beer barrel at the equilibrium pressure at which the dissolution rate of the carbon dioxide gas to the beer is equal to the dissociation rate of carbon dioxide gas from the beer. The equilibrium pressure rises as beer temperature increases. When the internal barrel pressure is much lower than the equilibrium pressure, it becomes vapid beer with no bubble head. When the internal barrel pressure is much higher than the equilibrium pressure, beer becomes too bubbly and too bitter.
When the beer is stored at the normal temperature, it is preferable that the storage temperature is 25.degree. C. or lower. When the storage temperature exceeds 30.degree. C., the beer loses its flavor quickly. The aforementioned equilibrium pressure is 3 to 4 kg/cm.sup.2 for the beer temperature of around 25.degree. C., and 1 to 2 kg/cm.sup.2 for the beer temperature of 10.degree. C. or lower.
If a replaced beer barrel has not been sufficiently cooled before vending, vapid beer will be served. If the gas regulator 2 has been adjusted such that the internal pressure in the beer barrel at the secondary side is raised to prevent the vapid beer, the internal pressure of the beer barrel will be too higher than the equilibrium pressure after the beer is sufficiently cooled in the refrigerator of the vending machine. Therefore, the internal pressure of the beer barrel should be reduced into the equilibrium pressure.
However, the internal pressure of the beer barrel can not be reduced in the conventional beer vending machine, since the check valves 6a, 6b are disposed in the feeder piping on the upstream side of the beer barrels 7a and 7b. When the beer is served under the pressure much higher than the equilibrium pressure, the amount of served beer will vary from cup to cup because of too many bubbles. Therefore, while the beer is not cooled sufficiently, there is no way but to vend vapid beer without pressurizing the beer barrel or to stop vending and wait until the new beer barrel is cooled sufficiently. Thus, the beer with poor quality will be served or sales chances will be lost.
In view of the foregoing, it is an object of the invention to provide a beer vending machine, which facilitates vending a predetermined amount of beer with a constant bubble head.
It is another object of the invention to provide a beer vending machine, which facilitates meticulously pressurizing the beer barrel under the equilibrium pressure corresponding to the beer temperature.
It is still another object of the invention to provide a method of pressurizing the beer barrels in the vending machine which facilitates pressurizing the beer barrel under the equilibrium pressure corresponding to the beer temperature.